None.
Not applicable.
The present invention generally relates to product marking and identification and more specifically to the marking of hot glass, as typified by picture tube components.
There is a need to piece identify hot glass articles. Picture tube components, for example panels and funnels, start life by being solidified in one of several, say 10, molds. Each piece contains mold related dimensional defects and is uniquely stressed as it is handled, cooled, and then annealed. Of the initially molded pieces, typically more than 30% never have the dimensional accuracy and strength to make it out of the plant.
This 30% loss is tolerable only because the broken (cull) glass can be recycled (one or more times) and, in fact, contributes to a better breed of glass. However, the scrap loss becomes very costly if much processing is done prior to scrapping.
Piece tracking will permit the plant operator to test and update the database for each piece and, thereby, determine if its history supports being scrapped rather than processed.
Suppose that the plant operator knew that mold #7 (and its associated shell) currently was producing dimensionally defective pieces and that they should be scrapped at the lehr exit, where they are known to be xe2x80x9cdead on arrivalxe2x80x9d. The downstream costs of processing these parts, through to the first gauging point, could be saved. This, of course, is a simplistic example, because the reason for known defects commonly may involve the interaction of two (or more) machines prior to annealing. The only way such interactions can be discovered quickly is through individual piece tracking.
In the mold #7 hypothetical, the average production rate is assumed to be 5 pieces/minute and that the costs associated with unnecessary post lehr processing is $4.00/piece (this figures includes labor, equipment amortization, consumables (e.g., grinding and polishing materials), maintenance, power, technical support, gauging costs, etc.). If the plant operator can scrap the 10% of production (those pieces formed by mold #7 or another currently defective mold) prior to downstream processing, the plant operator will save over $2.00/minute (approximately $500,000/year). If the post lehr processing equipment throughput is in fact limiting on plant production (especially when a machine is down), the savings can be significantly higher, because a xe2x80x9cgoodxe2x80x9d shippable piece can replace every predictably xe2x80x9cdeadxe2x80x9d piece. An additional good piece, of course, is worth far more than $4.00. The beneficial results of piece tracking include more production throughput and a savings when the operator eliminates unnecessary processing of bad pieces.
A variety of techniques for marking hot glass (picture tube panels and funnels) as they exit the forming mold at between about 400xc2x0 and 650 xc2x0 C. can be envisioned. These techniques are listed below along with the problems associated with each:
Thus, all of the tabulated approaches lead to complicated, difficult to maintain and/or messy equipment. A new approach to labeling hot glass for identification, therefore, is needed.
Method for marking hot glass article having a surface uses a flexible carrier ribbon bearing a laser ablatable, high temperature, diffusely reflective coating, preferably white in color. A pattern is imaged in said coating on carrier ribbon by laser ablation. The patterned carrier ribbon is pressed against the surface only for a time adequate for transferring the patterned coating to the surface. The carrier ribbon then is released from pressing against the surface. A xe2x80x9cpatternxe2x80x9d for present purposes includes alphanumeric characters, numbers, graphics, and bar codes (e.g., laser scanable and vision system readable bar codes).